In recent years heart-rate variability has become a topic of major interest, both in physiology and in psychology. One reason for the interest is that heart-rate variability is attributed to the balance between the parasympathetic and the sympathetic nervous system, respectively decreasing and increasing the heart rate. Beyond clinical interest there are known applications for use with a subject, including decreasing the sleep-onset time, yoga exercises, lowering the blood pressure, relaxation during computer use or television watching, vehicle driving, medicine, and sports situations.
The connection between being relaxed via meditation and breathing is shown in studies on the impact of meditation on cardio-respiratory synchronization with respect to breathing oscillations and the modulations of heart rate induced by respiration, known as respiratory sinus arrhythmia (RSA). Zen meditation synchronizes the cardio-respiratory interaction with respect to breathing oscillations and the heart rate variations induced by respiration. Furthermore, such meditation also drastically increases low-frequency variations of heart rate. Spontaneous breathing patterns hardly showed any cardio-respiratory synchronization and during mental activity the cardio-respiratory synchronization was decreased compared to both types of Zen meditation. It may also be shown that this kind of cardio-respiratory synchronization is advantageous for the gas exchange in the respiratory tract. Furthermore, it is known that this kind of religious practice has immediate physiological effects on cardio-respiratory interaction without the need of special long-term training. For yoga similar results are obtained.
Before 1964, the only method to control the respiratory induced variation was for the subject or patient to hold his breath. In 1964, the first known solution to the respiratory variations in the electrocardiogram/vector cardiogram (ECG/VCG) was in a paper Otto Schmitt published on techniques for signal averaging. In this paper, subjects were signalled using a light or sound to breathe, synchronized at a sub multiple of their heart rate. The signal was created from the ECG by counting, for example, two beats for the inspiration signal and the next three beats for the expiration signal. Each of the beats or time intervals with the same position in the respiratory cycle (i.e., first, second, third, etc.) were computer averaged to eliminate noise and other variations that occur unsynchronized with the heart beat. This resulted in a very noise-free signal representing respiratory sinus arrhythmia (RSA) changes in the beat-to-beat heart rate or RR interval. The non-respiration variations are reduced as the square root of number of breath cycles.
According to one aspect of the invention, a primary station comprises an array A current product is RESPeRATE®, which is a portable electronic device that helps lower blood pressure naturally by device-guided breathing. The device uses the body's natural tendency to follow external rhythms, interactively guiding the subject to reduce their breathing rate to a “therapeutic zone” of fewer than ten breaths per minute. This is the only medical device clinically proven to lower blood pressure through paced breathing therapy and is available for sale without a prescription.
A more complex system is disclosed in United States of America Patent Application Publication US 2005/0187426, which discloses a system and method for synchronizing the heart rate variability cycle with the breathing cycle. This publication describes a method and system for achieving coherence of heart rate variability by synchronizing the heart rate variability cycle to the breathing cycle and by consciously synchronizing the breathing cycle with an external reference that is closely aligned with the frequency of the natural heart rate variability cycle. Various means of representing the cycle of the external reference are provided including visual, audible, and sensory indicators. An instructive method is provided that teaches the subject to consciously synchronize their inhalation with the positive going aspect of the external reference cycle and their exhalation with the negative going aspect of the external reference cycle.
All of the presently known systems lack sufficient flexibility in the guidance system presented to the subject.